Method for lining underground pipelines

ABSTRACT

A method for renovation of pipelines, comprising introduction of lining layers into the existing pipeline, the lining layers corresponding in length to the length of the pipeline to be renovated. The lining layers consist of fusible polymers and are presurized and fused together by the introduction of a heat source into the inside of the innermost lining layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for renovation of undergroundpipelines preferably for sewage, comprising introduction of a liningpipe into an existing pipeline, said lining pipe having a lengthcorresponding to the length to be renovated, and consisting of a fusablepolymer in a folded condition, and unfolding of the lining pipe in orderto line the pipeline.

2. Description of the Invention Background

Folded pipes have already been used for lining pipelines for exampleaccording to SE-911948-9, where above all a combination of PE and PVChas given the prerequisites of the use of the concept relating to foldedpipes. The basic concept of this technique is that a length of coiledprefabricated folded pipe material without transverse welding istransported successively into e.g. a manhole and is located in anexisting pipeline to be lined, said pipeline connecting to the manhole.Introduction of a pipe in a folded condition makes possible to line witha pipe having the same outside diameter as the inside diameter of theexisting pipelines. Thereby the capacity of the pipeline substantiallycan be maintained, no additional arrangements for fixing the pipe in itslongitudinal direction being required and the connection of so calledservice pipelines being facilitated. When lining larger pipelines (Ø≧300mm) this technique has, however, not been possible to use, mainly due todifficulties in handling folded pipes of souch dimensions. This as aconsequence of larger handling forces being required as well as problemswith cracking in the fold areas of the pipes of larger dimensions.Moreover, the coils of the folded pipes have also been difficult, if notimpossible, to handle in a normal environment, not the least of which istransportation on a truck, as a consequence of the dimensions of thefolded pipes. This means, generally speaking, that the diameter of sucha coil be in order not to require special transport, must not be largerthan 2400 mm. In order to unfold lining pipes according to conventionalmethods it has also been necessary to preheat the lining pipe to atemperature of between 100° C. and 120° C. Moreover, at the lowertemperature it has been necessary to apply an inner over-atmosphericpressure of about 5 bar, which for large dimensions sets high demands onsecurity arrangements around the lining operation.

SUMMARY OF THE INVENTION

According to the invention described herein there is presented asolution to the problem of lining existing underground pipelines havinga diameter >300 mm with a continuous lining pipe introduced into thepipeline, the lining pipe being built up by introducing lining layersinto the pipeline to be lined, pressurising the layers and successivelyfusing them together by exposing each layer to fusion heat from a heatsource which is carried along the inside surface of the innermost layerof the lining built up so far. The consecutively introdused lininglayers may alternately be opaque and translucent to heating enegy tomake fusion of more than two layers possible in one fusion step.

The method described makes it possible to line existing pipelines havinga diameter up to at least 800 mm.

By the use of the method and the use of a smaller relative wallthickness equipment, such as coils of lining material etc., will be leasbulky and easier to handle.

It will also be possible to build up the pipe wall material for anyapplication in an environmentally or cost optimised way so that only theouter layer may provide structural tensile properties and durability,while intermediate layers may provide only tensile properties and theinner layer/layers may be adapted to the medium the pipline is intendedfor. A proper example is the use of PEX (Cross-linked Polyethylene)crosslinking during fusion after its introduction into the pipeline.Another example is the use of a foam as one of the layers, which iscaused to react by means of fusion heat.

A lining according to the invention eliminates the risk for subsoilwater penetrating between the existing pipeline and the lining due tothe existing pipeline being in a too bad condition. In the worst casethis may lead to the lining floating on the surface of the water withthe consequence that sooner or later it may rupture due to abrasion orfatigue.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail below with reference toan embodiment shown in the accompanying drawings, in which:

FIG. 1 schematically illustrates the principle for introducing a foldedlength of lining into an existing pipeline via a manhole,

FIG. 2a is a diagrammatic cross sectional view of through a reliningpipe in a folded condition,

FIG. 2b is a view corresponding to that one in FIG. 2a, wherein thelining has been unfolded,

FIG. 3a is a cross sectional view of the pipeline illustrating how threeunfolded lining layers are melted together, and

FIG. 3b is a view corresponding to FIG. 3a illustrating how threealready integrated layers are melted together with forth and fifthlayers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 generally illustrates the method of passing a folded first lininglayer 1 into a manhole 2 and into a pipeline 10 to be lined. With theaid of FIG. 1 it will be understood how the lining layer 1 in itsentirety is introduced into the pipeline 10 to be lined up to the nextcorresponding manhole (not shown). However, FIG. 1 does not show thatthe layers are so thin (between 1 and 5 mm, preferably about 3 mm) thatthey do not require heating in order to be able to be passed down asrequired according to the state of the art. The material in itself isflexible enough. After the first layer 1 having been located, said layerpreferably being translucent, the folded lining layer is sealed at bothends and then an inner over-pressure of up to 1.5 bar is applied. As aconsequence thereof the layer will be unfolded and will be pressedagainst the inside surface of the existing pipeline 10. Thereafter theseal of the lining layer is opened at one of its ends and another lininglayer 4, this time preferably opaque, is introduced and unfolded byover-pressure as previously described. When introducing the second andnext layers, a plug (not shown) that tightens against the precedinglayer can be used, which also can be driven through the pipeline bypressure. Then a further preferably translucent lining layer 5 isintroduced in the same manner, and after at least one end seal havingbeen opened (this is possible because the material in this condition hassufficient shape stability), a self-propelled heating device 3 (see FIG.3), emitting infrared light, is driven back and forth inside the lining,whereby the innermost translucent layer 5 in the pipeline by meltingtogether with the adjacent opaque layer 4 as a consequence of heatemission also brings the outermost layer to such a temperature that alsothe layers 1 and 4 melt together. During the heating phase, the pressureis maintained in the pipeline in order to press the liner against thepipeline and to create the necessary welding/fusing pressure between thelayers. At the same time (pressurised) air is circulated in the pipe toventilate possible reaction gases. When the three first layers 1, 4, 5have been located and melted together in the pipeline to be lined,lining layers 6, 7, 8, 9; . . . etc. are introduced two and two, firstpreferably an opaque layer and then preferably a translucent layer,whereafter heating as mentioned above is carried out, said introductionand heating operations being repeated until a required wall thickness ofthe completed lining pipe has been obtained.

In FIG. 2a it can be seen how a lining pipe layer 1, 4, and 5, etc. ofthe kind referred to is folded in the folded condition thereof when itis introduced into the pipeline to be lined. Moreover, it can be seenFIG. 2b how the first relining layer fits snugly against the insidesurface of the pipeline. The layers 4, 5, then inserted in the same wayfit snugly against the adjacent outside layer and are consequentlyaccurately dimensioned in lining steps. It is also possible to use oneor more lining layers that are coextruded, some of which may be textilereinforced. In FIG. 2b there is also shown in cross section hoses S₁ andS₂ which according to one embodiment of the invention are arranged inthe associated lining layer for the application of an inner overpressureas well as circulating gas, as mentioned above. The folding patternshown in FIG. 2 according to a modified embodiment may be more closelysimilar to a traditional firehose, in other words it is more or lesscompletely flat.

In FIG. 3 it is diagrammatically illustrated how the self-propelledheating device 3 for said welding operation is constructed in accordancewith a preferred embodiment. The heating device 3 comprises a chassiswith driven wheels having a device mounted thereon which when activatedtogether with the associated power and drive unit F, emits heatradiation preferably in the short wave infrared area. Due to theambition to avoid IR-radiation absorption peaks, the wavelength rangesfrom 0.7 to 1.5 μm, and is preferably in the region of 1.15 μm, whereinthe infrared radiation is the most intense per unit of time. Thefiltered wavelength and different absorption properties of the lininglayers together prevent both the inner surface of the liner from beingheated too much and the heating energy from being directed to the innerlayer(s). The device mounted on the chassis extends in the longitudinaldirection of the pipe in order to have an omnidirectional effect. Theheating device may be driven from the one or the other end of therelining pipe. It is, however, an advantage if the heating device canroll on a surface having normal surrounding temperature.

What is claimed is:
 1. Method for renovation of a length of a pipelinecomprising introduction of a lining pipe into an existing pipeline, saidlining pipe having a length corresponding to a length to be renovatedand consisting of fusible polymer lining layers in a folded condition,and unfolding of the lining pipe in order to line the existing pipeline,comprising the steps of building up said lining pipe by successivelyintroducing said lining layers (1,4,5,6,7,8,9) in the existing pipelineto be lined, successively pressuring said lining layers and fusing themtogether by exposing said lining layers (1, 4-9) to fusion heat from aninfrared heat source (3), wherein said lining layers are alternatelyopaque and translucent to infrared heating energy from said infraredheat source (3), and wherein said infrared heat source (3) is carriedalong an inside surface of an innermost layer of said lining pipe builtup so far.
 2. Method according to claim 1, wherein at least one of thelining layers comprises PEX, and is cross-linked after its introductioninto the existing pipeline.
 3. Method according to claim 2, wherein thecrosslinking is achieved during fusing of the lining layers.
 4. Methodaccording to claim 1 wherein two lining layers are introduced at thesame time in the existing pipeline to be lined.
 5. Method according toclaim 1 wherein after the introduction of the lining layers (1,4) andafter said lining layers having been subjected to pressure the pressureis at least to some extent lowered before the lining layers are fusedtogether by means of a heating device, which is introduced at one of theends of the lining layers.
 6. Method according to claim 1 wherein thelining layers are adapted to the intended use of the existing pipelineby using differing materials for the lining layers depending on theradial position thereof.
 7. Method according to claim 1 wherein at leastone of the lining layers is a foam layer, which is caused to react bymeans of heating to fuse the foam layer.
 8. Method according to claim 1,wherein use is made of IR wavelengths in the range of 0.7 to 1.5 μm. 9.Method according to claim 8 wherein coextruded layers are used. 10.Method according to claim 9, wherein one or more of said coextrudedlayers are textile reinforced.
 11. Method according to claim 8 whereinthe lining pipe at least partly comprises several independent layerswhich are fused together.
 12. Method according to claim 1 wherein thelining layers are opaque and translucent alternately and that the heatsource (3) is employed along at least every third lining layerintroduced.
 13. Method according to claim 1 wherein the lining layersare introduced into the existing pipeline through a manhole and whereinthe ratio between an outside diameter and a wall thickness of the lininglayers are less than 100.